Intussusception

Intussusception occurs when one segment of bowel slides into the adjoining segment, like a collapsible tube being pushed inside itself. The trapped bowel becomes narrowed, causing intermittent obstruction. Mesenteric veins and lymphatic vessels are compressed first, producing bowel-wall edema; as pressure increases, arterial flow can fall, leading to ischemia, necrosis, perforation, peritonitis, and shock. This progression explains why the child may look surprisingly well between painful episodes and then deteriorate quickly. The bowel is not continuously obstructed at first, and the child may temporarily recover when the telescoped segment partially relaxes. Persistent obstruction and tissue injury eventually produce more constant vomiting, distention, bleeding, and systemic illness. Most cases occur between 6 months and 3 years of age, with peak incidence between 5 and 10 months. Infants and young children may not localize pain or describe nausea, so behaviour often provides the first clinical information. Sudden pallor, lethargy, inconsolable crying, or repeatedly drawing the knees toward the abdomen may be more revealing than the child’s words.